Dark, cold and whipped by supersonic winds, Neptune is the last of the hydrogen and helium gas giants in our solar system. More than 30 times as far from the sun as Earth, the planet takes almost 165 Earth years to orbit our sun. In 2011 Neptune completed its first orbit since its discovery in 1846.

10 Need-to-Know Things About Neptune:

If the sun were as tall as a typical front door, the Earth would be the size of a nickel and Neptune would be about as big as a baseball.

Vertical relief in Neptune's bright cloud streaks.

Neptune orbits our sun, a star. Neptune is the eighth planet from the sun at a distance of about 4.5 billion km (2.8 billion miles) or 30.07 AU.

One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). Neptune makes a complete orbit around the sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days).

Neptune is a sister ice giant to Uranus. Neptune is mostly made of a very thick, very hot combination of water (H2O), ammonia (NH3), and methane (CH4) over a possible heavier, approximately Earth-sized, solid core.

Neptune's atmosphere is made up mostly of hydrogen (H2), helium (He) and methane (CH4).

Neptune has 13 confirmed moons (and 1 more awaiting official confirmation of discovery). Neptune's moons are named after various sea gods and nymphs in Greek mythology.

Neptune has six rings.

Voyager 2 is the only spacecraft to have visited Neptune.

Neptune cannot support life as we know it.

At times during the course of Neptune's orbit, dwarf planet Pluto is actually closer to the sun, and us, than Neptune. This is due to the unusual elliptical (egg) shape of Pluto's orbit.